Turritella Designs

When I began enamelling, I was introduced to a few cardinal rules, including:

1) Always clean your enamel of the ‘fine’ particles, or transparent enamel will be cloudy when it is fired.

2) Be careful not to over-fire your copper and silver cloisonné pieces, or you may accidentally create a eutectic reaction.

I decided to do some tests yesterday, to see what would happen if I blatantly broke these rules.

Extra fine enamel (2020 Flux for Silver) over copper

When I prepare my enamels, I use stacking sifters to separate the fine particles from the larger 325 mesh grains that I use for wet-packing applications. I usually save the fine enamel powder for painting, so there is no waste. When the fine powder is used for painting, it fires cleanly, though I suspect this is because the powder is applied in such thin layers.

When I applied a thick layer of fine 2020 Flux for Silver over a copper blank, the fine enamel created an unexpected crackle-like pattern in between areas full of very fine bubbles. The result was cloudy, as the rule had suggested it would be, but I hadn't expected the crackle pattern.

I suspect the pattern in the fine bubbles is the result of the piece experiencing heat-shock as it comes up to the fusing temperature inside the kiln. Quite often, if you open a kiln a few seconds after placing a piece inside, you can see fused areas of enamel crack and then re-fuse in response to temperature change as the piece comes up to 1500F from room temperature. I think the fine bubbles trapped in the enamel burst along these cracks and left the crackle pattern behind when the glass fused again.

Eutectic reaction of silver wires over a copper base

A 'eutectic reaction' is a reaction between metals, such as fine silver and copper, which creates an alloy that has different properties from either parent metal. Cloisonné wires normally sit atop a layer of enamel on a metal base. If the cloisonné wire directly touches the copper metal base, an alloy will form, dissolving the thin cloisonné wire and making the enamel pool strangely against the metal.

In the above photo, you can see ghostly lines where the cloisonné wires were originally placed. The alloy can clearly be seen beneath the enamel, but it only caused one gap to open in the enamel surface. It was reassuringly difficult to create this reaction. I fired the piece up to 1560F and held it there for about three minutes to get this result. I peeked in the kiln a few times to find the reaction progressing slowly. The wires melted gently into the copper base.

I found these experiments to be a very interesting exercise. It's good to know what the results will be when you choose to break the rules.